A Unified, Self-Consistent Theory for the Plastic-Creep Deformation of Metals

A unified, self-consistent scheme is formulated to determine the plastic-creep behavior of metals under combined stress. It is pointed out that such a deformation involves the transition from the inhomogeneity to transformation problem in the sense of Eshelby. The plastic deformation is studied by the Berveiller and Zaoui modification of Hill’s model. Following plastic deformation the structure of self-consistent relation for subsequent creep is analyzed and found to be independent of prior plastic strains. These self-consistent relations are used in conjunction with one set of unified constitutive equations for slip systems, in which the effect of prior plastic strains on the subsequent creep is considered. This unified, self-consistent scheme is applied to predict the plastic-creep strains of a 304 stainless steel. As compared to the experimental data, the self-consistent scheme is found to consistently provide reasonably accurate estimates for the total inelastic strains, while the predictions by the von Mises theory are seen to be less favorable.